One Good Medical Part Deserves Another

Excellent facilities and advanced CAM spurs start-up medical part manufacturer’s growth

“We just got a print in of a prototype a couple of days ago. Years ago we’d look at the print and think it was a nightmare, like a 5th grader looking at Mozart sheet music. But now you look at it and say, ‘I think I’ll start on this end’. You kind of dive into it. We know we can generate the toolpaths to machine it.”

Those were the words Lou Dertouzos used to describe what the transition from traditional aerospace to advanced medical parts manufacturing was like for him. Lou spent most of his career (about 30 years) in aerospace manufacturing and even had his own shop. Five years ago he was lured away by a major medical device manufacturer in Indiana. For the past year he has been engineering manager for Innovative Medical (Fort Myers, FL), a start-up machine shop specializing in the manufacture of surgical tools and implants.

He explained that designers of aerospace parts, at least in the past, generally designed within the constraints of typical high-performance CNC machining capabilities. Medical device designers don’t seem to look at it that way. They don’t perceive any limits. Whatever material and geometry combinations they can create in CAD, and prove out with finite element analysis, is what they expect their suppliers to produce and deliver on time.

Innovative Medical, now in its second year, was conceived specifically to take on that sort of challenge. The owners, Youngquist Brothers Inc., spared no expense in equipping this brand new, 21,000-square foot plant with 20 CNC machines, including Willimen-Macodel mill-turn systems and Citizen Swiss turning machines. Advanced Mycrona multi-sensor CMMs verify that parts have been manufactured to spec. As for delivering on time, the owners equipped the plant with its own generator and an uninterruptible power supply to make sure thatthere would be absolutely no excuses. To run the plant, Youngquist Brothers recruited experienced medical manufacturing professionals from all over the country, which is where Dertouzos came in.

Off and Running
One of the businesses Youngquist Brothers operated was a machine shop that was established in 1982. Medical manufacturing was, however, an entirely new market and Innovative Medical was a separate and entirely different company. Because it was new and different, some of the professional talent at the new shop, Dertouzos included, expected that there would be plenty of time to methodically develop its workflow processes as the business gradually took off. No such luck. As customers discovered that Innovative Medical could expeditiously reproduce their difficult prototype designs, a backlog of work ensued. Dertouzos, who is responsible for programming the Willimens, found himself with more work than he could handle with the company’s existing CAM system.

He convinced management to purchase two seats of Mastercam (from CNC Software, Inc., Tolland, CT), a CAM program he had been using since the mid ‘80s. Soon he was keeping the company’s 15 Willimens entirely busy and discharging his other responsibilities as engineering manager. Dertouzos’ most recent experience had been with Mastercam Version 9. Innovative Medical purchased two seats of Mastercam X2. “It was a big leap as far as the software goes,” he said.

“Because of the workload, I was not able to get any formal training. I couldn’t have anyone come in to show me; I had to figure it out on my own. Within the first day, I was already putting toolpaths on the parts, and soon I could create toolpaths so complex you’d be amazed that the machine could even keep up with it.”

“No Limits” Mentality
During the past year, Dertouzos has assimilated the “no limits” mentality of his medical design engineer customers. “I have yet to find a part that I could imagine (or see as a CAD model) that I could not cut in Mastercam. A case in point is a part with a spiral undercut intended to lock a bone screw into a surgical implant. “When you first look at it, you don’t know how the heck you can cut it. I stared at it for five minutes because I had never done that kind of motion before. Then I started looking through the sample files--Mastercam has hundreds of them. Voila, there it was, exactly the cut I needed to make. We do it with a continuous 5-axis motion using a lollipop tool.”

According to Dertouzos, one of the interesting things about Innovative Medical is that the layout of the shop does not include any manufacturing cells. That is because the 5-axis mill-turn machines produce a wide range of medical parts from continuously fed bar stock and do it all in one setup. The machines themselves (which are rumoured to be in use at the Rolex watch factory) are capable of extremely close tolerances (for example, ±0. 0005” holes for end milling). A detailed machine definition contained in Mastercam’s memory complements this by reducing potential stacking errors.

So with productivity and precision now a given, his greatest concern is making the intricate cuts called for in the customers’ CAD models. Mastercam’s suite of high-speed machining toolpaths has provided the capabilities needed to transform the customers’ unique designs into physical reality. Some examples of Mastercam features that give Innovative Medical the muscle it needs include:

More Control. Dertouzos observes that many CAM packages expect the user to highlight the part and tell the software to generate the toolpaths. He does not appreciate this approach. Because of his depth of manual machining experience, he prefers Mastercam’s ability to be able to take control of the programming wherever he wants to optimize material removal.
Material Volume Feedback. On the other hand, Mastercam provides him with unique automated tools that allow him to make important decisions to increase outputs and improve equipment and tool life. For example, the software actually calculates how much material will be removed during a given step. This, in turn, allows him to set tool engagement limits so that the machine doesn’t go from taking a light cut to suddenly plunging into the part. This feature also provides feedback that allows for increasing feeds and speeds on straight cuts to improve throughput.
On-Machine Surface Finish. Using toolpaths that produce precision surface finishes without taking the part off the machine eliminates subsequent tumbling or vibratory finishing operations. “We just glass bead it like the customer asks us to and it’s ready to ship. This is a real time saver.”
Edge Breaks. Cosmetics are essential to medical part manufacturing, so CAD models frequently show numerous edge breaks that Douterzos creates in Mastercam. The alternative would be having a person spend hours manually scraping the parts.
The Pigtail Part. A recent job required Innovative Medical to make a curled part that reminded him of a pigtail. To the naked eye, it did not appear to be structurally sound, but Finite Element Analysis confirmed that it was, as long as it was manufactured with no sharp edges or mismatches between surfaces that could create fracture points. Using the Mastercam-generated toolpaths, the Willemen performs these cuts all in one setup with the cutter rarely leaving the surface of the workpiece. “The machine never slows down, it never stops, it goes crazy making the part,” Dertouzos said.
Making Apples from Oranges. It can take a day or more to program a complex prototype part and manufacture it, but that’s not the end of the story. Revisions B, C, and perhaps D are sure to follow as night follows day. Fortunately, all or most of the creative toolpathing that went into the first version can be carried over to subsequent versions using Mastercam’s Change Recognition feature. It can automatically compare the new CAD model to the previous one and reorganize the old toolpaths to fit the new design circumstances. This means that toolpaths for new versions can be created, with a little tweaking, in a fraction of the time it took to create the original.

Dertouzos said, “A great example is a family of cervical plates we manufacture. They range in size anywhere from 12 mm to 115 mm. The basic shape just changes slightly, expands, and elongates. The first one took me nearly two days to get everything the way I wanted and machine it. Then I created the next program and made the part in less than a day. That is nearly unheard of. ”

The CAD software allows Dertouzos to perfect settings and toolpaths for one part program and save them generically in a special library. He said, “These library files have all the parameters, the size tool, the speed, the feed, and the stepover, but not the associated geometry. This allows you to pull the guts from another program that worked well and adhere it to a different model as often as needed. So I don’t have to sit there and re-think everything. It is so clearly laid out. That’s part of the reason that these jobs get pumped out so quickly.”

Recently, Dertouzos was backing up his files so that he could safely change to a new computer, and he discovered that he had written about 800 Mastercam programs during his first year at Innovative Medical.

“What I particularly love about that is that someday soon a customer will call me about a part he needs recreated from his model, but he’s not sure anyone can do it. Then I will say, ‘but last year we did this one that was something like it.’ Then he will say ‘Okay. Let’s go.’”